Mr Lansley said: “When you talk to people about their concerns for the future, it’s evident that dementia is a bigger concern even than having cancer.

“The loss of personality and memory – these are the things people find desperately tough to ­contemplate, both for themselves and their loved ones. What’s important is if we can give people hope that in the future, we will increasingly be able not only to identify dementia but to treat it.”

Mr Cameron will today say it is a “scandal” that the UK has not done more to address dementia, which affects 670,000 people. Another 400,000 have not been diagnosed and do not know they have it. The cost to UK society is estimated at £23billion.

Mr Cameron will say: “Dementia is simply a terrible disease. And it is a scandal that we as a country haven’t kept pace with it.” He will add: “We need an all-out fight-back against this disease. One that cuts across society.”

Shirley Cramer, acting chief executive of Alzheimer’s Research UK, said: “David Cameron’s announcements are a turning point in our battle to defeat dementia.”